The action of the novel gastrointestinal prokinetic prucalopride on the HERG K+ channel and the common T897 polymorph

Prokinetics-safety and efficacy: The European Society of Neurogastroenterology and Motility/The American Neurogastroenterology and Motility Society expert review

BACKGROUND

Prokinetics are a class of pharmacological drugs designed to improve gastrointestinal (GI) motility, either regionally or across the whole gut. Each drug has its merits and drawbacks, and based on current evidence as high-quality studies are limited, we have no clear recommendation on one class or other. However, there remains a large unmet need for both regionally selective and/or globally acting prokinetic drugs that work primarily intraluminally and are safe and without systemic side effects.

PURPOSE

Here, we describe the strengths and weaknesses of six classes of prokinetic drugs, including their pharmacokinetic properties, efficacy, safety and tolerability and potential indications.

Pharmacological and nutritional therapy of children and adults with chronic intestinal pseudo-obstruction

INTRODUCTION

Chronic intestinal pseudo-obstruction (CIPO) is a rare, heterogeneous and severe form of gastrointestinal dysmotility.

AREAS COVERED

Pertinent literature on pediatric and adult CIPO management has been assessed via PubMed, Scopus, and EMBASE from inception to June 2022. Prokinetics, aimed at restoring intestinal propulsion (e.g. orthopramides and substituted benzamides, acetyl cholinesterase inhibitors, serotonergic agents and others), have been poorly tested and the available data showed only partial efficacy. Moreover, some prokinetic agents (e.g. orthopramides and substituted benzamides) can cause major side effects. The CIPO-related small intestinal bacterial overgrowth requires treatment preferably via poorly absorbable antibiotics to avoid bacterial resistance. Apart from opioids, which worsen gut motility, analgesics should be considered to manage visceral pain, which might dominate the clinical manifestations. Nutritional support, via modified oral feeding, enteral or parenteral nutrition, is key to halt CIPO-related malnutrition.

EXPERT OPINION

There have been significant roadblocks preventing the development of CIPO treatment. Nonetheless, the considerable advancement in neurogastroenterology and pharmacological agents cast hopes to test the actual efficacy of new prokinetics via well-designed clinical trials. Adequate dietary strategies and supplementation remain of crucial importance. Taken together, novel pharmacological and nutritional options are expected to provide adequate treatments for these patients.

Opioid-induced constipation: a narrative review of therapeutic options in clinical management

Pain therapy often entails gastrointestinal adverse events. While opioids are effective drugs for pain relief, the incidence of opioid-induced constipation (OIC) varies greatly from 15% to as high as 81%. This can lead to a significant impairment in quality of life, often resulting in discontinuation of opioid therapy. In this regard, a good doctor-patient relationship is especially pivotal when initiating opioid therapy. In addition to a detailed history of bowel habits, patient education regarding the possible gastrointestinal side effects of the drugs is crucial. In addition, the bowel function must be regularly evaluated for the entire duration of treatment with opioids. Furthermore, if the patient has preexisting constipation that is well under control, continuation of that treatment is important. In the absence of such history, general recommendations should include sufficient fluid intake, physical activity, and regular intake of dietary fiber. In patients of OIC with ongoing opioid therapy, the necessity of opioid use should be critically reevaluated in terms of an with acceptable quality of life, particularly in cases of non-cancer pain. If opioids must be continued, lowering the dose may help, as well as changing the type of opioid. If these measures do not suffice, the next step for persistent OIC is the administration of laxatives. If these are ineffective as well, treatment with peripherally active μ-opioid receptor antagonists should be considered. Enemas and irrigation are emergency measures, often used as a last resort.

An update on prucalopride in the treatment of chronic constipation

Chronic constipation (CC) is a highly prevalent and often under-appreciated gastrointestinal disorder associated with significant impairment in quality of life. Symptoms of constipation are typically present for a number of years prior to a patient seeking help. Lifestyle modifications followed by, or coupled with, over-the-counter laxatives represent the initial treatment option; however, relief for many is limited and dissatisfaction rates for these approaches remain high. Over recent years, therefore, considerable effort has been exerted on the development of novel pharmacological approaches. Two major targets have emerged, motility and secretion. Research on the former led to the development of a number of prokinetic agents capable of stimulating colonic motility and, thus, accelerating colonic transit. Of these, earlier prototypes such as cisapride and tegaserod, though effective, were ultimately withdrawn due to cardiovascular adverse events due in part to receptor non-selectivity. Highly selective serotonergic receptor agonists have since emerged which appear to be equally effective in stimulating gut motility but are devoid of cardiac side effects. One such agent is prucalopride, which has now been approved for the management of chronic idiopathic constipation in several countries, but not in the United States. Multiple multicenter, randomized placebo-controlled clinical trials have demonstrated superiority for prucalopride compared to placebo in the short to medium term in relieving the major symptoms of constipation in both men and women across a broad spectrum of ages, ethnicities and geographic locations. To date, prucalopride has enjoyed a favorable safety profile and there have been no signals to suggest arrythmogenicity. Efficacy over longer periods of treatment remains to be confirmed. Evidence for efficacy in other forms of constipation, such as opioid-induced constipation and that related to Parkinson's disease is beginning to emerge; its status in the management of constipation-predominant irritable bowel syndrome or foregut motility disorders, such as gastroparesis, remains to be established.

Prucalopride: A Review in Chronic Idiopathic Constipation

Prucalopride (Resolor®), a highly selective serotonin 5-HT4 receptor agonist, is indicated in the European Economic Area for the treatment of adults with chronic idiopathic constipation (CIC) in whom laxatives have failed to provide adequate relief. This article reviews the pharmacological properties of prucalopride and its clinical efficacy and tolerability in patients with CIC. In five well-designed, 12-week trials in patients with CIC, oral prucalopride 2 mg/day was significantly more effective than placebo at improving bowel function, including the number of bowel movements and a range of other constipation symptoms, as well as health-related quality of life and patient satisfaction; however, no significant differences in bowel function measures were observed between prucalopride and placebo in a 24-week trial. Oral PEG-3350 + electrolytes reconstituted powder was found to be noninferior but not superior to prucalopride according to primary endpoint data from a 4-week, controlled-environment trial. Prucalopride was generally well tolerated in clinical trials; the most common adverse events were headache, diarrhoea, nausea and abdominal pain. No cardiovascular safety issues have arisen with prucalopride treatment. Although further long-term and comparative data would be beneficial, prucalopride provides an additional treatment option for patients with CIC.

[Current issues on the treatment of chronic constipation]

Chronic constipation is a very common clinical problem with its prevalence of up to 14% in the general population. It is not a life-threatening disease, but since patient's satisfaction to the treatment is known to be as low as 50%, chronic constipation still remains a clinically challenging problem. Fortunately, many new treatments have been introduced or are to be introduced in the near future. This article will review the basic concepts and the results of recent studies on the new treatments for chronic constipation.

Efficacy and Safety of Prucalopride in Chronic Constipation: An Integrated Analysis of Six Randomized, Controlled Clinical Trials

BACKGROUND

Prucalopride, a selective, high-affinity 5-hydroxytryptamine 4 receptor agonist, stimulates gastrointestinal and colonic motility and alleviates common symptoms of chronic constipation (CC) in adults. The relative efficacy by gender has not been evaluated.

AIM

To evaluate the global efficacy and safety of prucalopride 2 mg daily in men and women with CC using data from six large, randomized, controlled clinical trials.

METHODS

Data were combined from six phase 3 and 4, double-blind, randomized, placebo-controlled, parallel-group trials. The primary efficacy endpoint was the percentage of patients with a mean of ≥3 spontaneous complete bowel movements (SCBMs) per week over 12 weeks of treatment. Safety was assessed throughout all the trials.

RESULTS

Overall, 2484 patients (597 men; 1887 women; prucalopride, 1237; placebo, 1247) were included in the integrated efficacy analysis and 2552 patients were included in the integrated safety analysis. Significantly more patients achieved a mean of ≥3 SCBMs/week over the 12 weeks of treatment in the prucalopride group (27.8 %) than in the placebo group [13.2 %, OR 2.68 (95 % CI 2.16, 3.33), p < 0.001]. Prucalopride had a favorable safety and tolerability profile. Efficacy and safety outcomes were not significantly different between men and women.

CONCLUSION

The integrated analysis demonstrates the efficacy and safety of prucalopride in the treatment of CC in men and women.

A randomized, double-blind, placebo-controlled, phase 3 trial to evaluate the efficacy, safety, and tolerability of prucalopride in men with chronic constipation

OBJECTIVES

Prucalopride is effective at alleviating symptoms of chronic constipation in women. The aim of this study was to assess the efficacy of 12 weeks of prucalopride treatment compared with placebo in men with chronic constipation.

METHODS

This was a multicenter, stratified, randomized, parallel-group, double-blind, placebo-controlled, phase 3 study (ClinicalTrials.gov identifier: NCT01147926). The primary end point was the proportion of patients with a mean of three or more spontaneous complete bowel movements (SCBMs) per week across the treatment period. Efficacy end points were assessed using daily electronic diaries, global assessment of the severity of constipation and efficacy of treatment, and Patient Assessment of Constipation-Symptoms (PAC-SYM) and Patient Assessment of Constipation-Quality of Life (PAC-QOL) questionnaires.

RESULTS

In total, 374 patients were enrolled in the study. Significantly more patients achieved a mean of three or more SCBMs per week in the prucalopride group (37.9%) than in the placebo group (17.7%, P<0.0001). The proportion of patients rating their constipation treatment as "quite a bit" to "extremely" effective at the final on-treatment visit was 46.7 and 30.4% in the prucalopride and placebo groups, respectively. The difference between treatment groups was statistically significant (P<0.0001). The proportion of patients with an improvement of at least 1 point in PAC-QOL satisfaction subscale score was 52.7 and 38.8% in the prucalopride and placebo groups, respectively (P=0.0035). Prucalopride had a good safety profile and was well tolerated.

CONCLUSIONS

Prucalopride is effective, has a good safety profile, and is well tolerated for the treatment of men with chronic constipation.

Efficacy and safety of prucalopride in adults and children with chronic constipation

INTRODUCTION

Chronic constipation (CC) is a debilitating condition with high prevalence rates both in children and adults. Despite the broad range of medical and pharmaceutical treatments, the bowel function does not restore in a fair amount of patients. Prucalopride is a first-in-class selective, high affinity serotonin 5-hydroxytryptamine type 4 (5-HT4) receptor agonist promoting gastro-intestinal prokinetic activity and has been evaluated for the treatment of CC.

AREAS COVERED

A PubMed search (1965 - 2014) using the following terms alone or in combination: prucalopride, 5-HT4, R093877, safety, toxicity, pharmacokinetics, pharmacodynamics, transit, cardiac, human ether-a-go-go related gene (hERG), arrhythmia, potassium current, elderly, children.

EXPERT OPINION

Prucalopride, a highly selective 5-HT4 receptor agonist, stimulates gastrointestinal motility and has been proven to be effective in the treatment of CC in adults by increasing stool frequency, reducing constipation-related symptoms and improving quality of life (QoL). The safety and tolerability have been proven to be excellent. More research would be preferable on the effect of prucalopride on men, children and in other gastrointestinal motility disorders.

Prucalopride: a review of its use in the management of chronic constipation

The highly selective serotonin 5-HT4 receptor agonist prucalopride (Resolor(®), Resotran(®), Resotrans(®)) is indicated for the treatment of chronic constipation. In four randomized, double-blind, multicentre, 12-week trials in patients (predominantly women) with chronic constipation, oral prucalopride 2 mg once daily improved bowel function to a significantly greater extent than placebo, with a significantly greater proportion of prucalopride than placebo recipients achieving an average of ≥3 spontaneous, complete bowel movements per week (primary endpoint). Significantly greater improvements in health-related quality of life, patient satisfaction with treatment and bowel habit, and a range of constipation-related symptoms were also seen with prucalopride than with placebo. Satisfaction with treatment and bowel habit was maintained with prucalopride in the longer term. Prucalopride was generally well tolerated in patients with chronic constipation, with the most commonly reported adverse events (headache, nausea, abdominal pain, diarrhoea) primarily occurring on the first day of treatment. During the clinical trials, no cardiovascular safety issues have arisen in patients with chronic constipation receiving prucalopride. In conclusion, prucalopride is an important option for use in patients with chronic constipation who have not experienced adequate relief with laxatives.

Comparative effects of Guanfu base A and Guanfu base G on HERG K+ channel

BACKGROUND

Guanfu base A (GFA) and Guanfu base G (GFG) are chemicals isolated from Aconitum coreanum. The potassium channel encoded by the human ether-a-go-go related gene (HERG) plays an important role in repolarization of the cardiac action potential. The purpose of the present study was to investigate the effects of GFA and GFG on the HERG channel and its structure-function relationship.

METHODS

The effects of GFA and GFG were investigated in human embryonic kidney 293 (HEK293) cells transiently transfected with HERG complementary DNA using a whole-cell patch clamp technique.

RESULTS

GFA and GFG inhibited HERG channel current in concentration-, voltage-, and time-dependent manners. The IC50 for GFA and GFG was 1.64 mM and 17.9 μM, respectively. Both GFA and GFG shifted the activation curve in a negative direction and accelerated channel inactivation but showed no effect on the inactivation curve. Moreover, GFG also accelerated channel recovery from inactivation.

CONCLUSIONS

Both GFA and GFG blocked HERG channel current. This effect was stronger after GFG treatment rather than GFA treatment. This blockade was dependent on open and inactivated channel states. These results indicate that GFA could be a rather promising antiarrhythmic drug without severe side effects, whereas GFG could cause QT prolongation and requires further research.

Assessment of the cardiac safety of prucalopride in healthy volunteers: a randomized, double-blind, placebo- and positive-controlled thorough QT study

AIMS

To assess steady-state effects of therapeutic and supra-therapeutic doses of prucalopride on the QT interval using a novel design involving a parallel placebo group with nested crossover for positive control.

METHODS

A double-blind, double-dummy, placebo- and active-controlled study was conducted in 120 healthy male and female volunteers (NCT00903747). Volunteers were randomized to receive prucalopride 2-10 mg once daily (therapeutic and supratherapeutic doses, respectively) (group 1), placebo with 400 mg moxifloxacin on day 1 (group 2a), or placebo with moxifloxacin on day 15 (group 2b). Twelve-lead 24 h Holter ECGs recorded at various time-points were evaluated blind and centrally.

RESULTS

Estimated mean difference in study specific corrected QT interval (QT(c)SS) time-matched change from baseline between prucalopride (2 and 10 mg) and placebo was <5 ms at all time points (maximum mean difference: 3.83 ms at 3.5 h post dose on day 5 with 2 mg [90% Cl -0.33, 6.38 ms]). Upper limits of the two-sided 90% CI for QT(c)SS were all <10 ms. There were no outlying QT(c)SS values >450 ms and no subjects had an increase >60 ms following prucalopride. Moxifloxacin produced the expected significant changes in QT(c)SS (>5 ms, maximum of +12.7 ms at 5 h post dose) at all time-points except 1 h post dose. Prucalopride resulted in small increases in heart rate (maximum of 5.8 beats min(-1)), which were similar for 2 and 10 mg. Prucalopride was well tolerated after first day of treatment.

CONCLUSION

Prucalopride at both therapeutic and supra therapeutic doses has no clinically significant effects on cardiac repolarisation in healthy volunteers.

Assessment of the cardiac safety of prucalopride in healthy volunteers: a randomized, double-blind, placebo- and positive-controlled thorough QT study

AIMS

To assess steady-state effects of therapeutic and supra-therapeutic doses of prucalopride on the QT interval using a novel design involving a parallel placebo group with nested crossover for positive control.

METHODS

A double-blind, double-dummy, placebo- and active-controlled study was conducted in 120 healthy male and female volunteers (NCT00903747). Volunteers were randomized to receive prucalopride 2-10 mg once daily (therapeutic and supratherapeutic doses, respectively) (group 1), placebo with 400 mg moxifloxacin on day 1 (group 2a), or placebo with moxifloxacin on day 15 (group 2b). Twelve-lead 24 h Holter ECGs recorded at various time-points were evaluated blind and centrally.

RESULTS

Estimated mean difference in study specific corrected QT interval (QT(c)SS) time-matched change from baseline between prucalopride (2 and 10 mg) and placebo was <5 ms at all time points (maximum mean difference: 3.83 ms at 3.5 h post dose on day 5 with 2 mg [90% Cl -0.33, 6.38 ms]). Upper limits of the two-sided 90% CI for QT(c)SS were all <10 ms. There were no outlying QT(c)SS values >450 ms and no subjects had an increase >60 ms following prucalopride. Moxifloxacin produced the expected significant changes in QT(c)SS (>5 ms, maximum of +12.7 ms at 5 h post dose) at all time-points except 1 h post dose. Prucalopride resulted in small increases in heart rate (maximum of 5.8 beats min(-1)), which were similar for 2 and 10 mg. Prucalopride was well tolerated after first day of treatment.

CONCLUSION

Prucalopride at both therapeutic and supra therapeutic doses has no clinically significant effects on cardiac repolarisation in healthy volunteers.

Prucalopride: the evidence for its use in the treatment of chronic constipation

Introduction:

Chronic constipation is a common condition that is difficult to treat. Existing options for the treatment of patients with different subgroups of constipation are limited. A new efficacious and safe drug is needed to limit the frequently observed adverse effects induced by laxatives, to improve general wellbeing and quality of life, and to provide an alternative for enemas or even resectional surgery in patients in whom stimulant laxatives cause disabling adverse effects or fail to increase bowel movement frequency.

Aims:

The purpose of this article is to assess the current evidence supporting the use of the selective and high affinity serotonin-4 (5-HT₄) receptor agonist prucalopride in the management of chronic constipation.

Evidence review:

There are now convincing data from phase II and multicenter phase III randomized, double-blind, placebo-controlled trials that prucalopride treatment results in a clinically meaningful increase in the number of spontaneous complete bowel movements, a reduction of perceived severity of symptoms and improved disease-related quality of life in a significant proportion of patients. There is a rapid onset of the effect and the improvement is maintained for at least 12 weeks.

Prucalopride in a dose of up to 4 mg per day appeared generally well tolerated and devoid of serious cardiac events. Adverse events, most frequently headache and nausea, are usually mild or moderate and occur mainly during the first days of treatment. Prucalopride should be used with prudence and with careful assessment of the benefit-risk ratio until more clinical and electrophysiologic data become available, because relatively few patients have been exposed to the drug for long periods of time.

Place in therapy:

Prucalopride 1–2 mg once daily may be given to patients suffering from chronic constipation for whom laxatives do not provide adequate relief of their symptoms. Patients with severe constipation and slow transit, who frequently develop tolerance to stimulant laxatives, are also eligible for prucalopride treatment.

Constipation, IBs and the 5-HT4 Receptor: What Role for Prucalopride?

After the problems associated with the non-selective 5-HT4 receptor agonists cisapride and tegaserod, the 5-HT4 receptor is now beginning to come in from the cold. Thus, prucalopride is now the first of a new class of drug defined by selectivity and high intrinsic activity at the 5-HT4 receptor. Prucalopride has been developed for treatment of chronic constipation rather than constipation-predominant irritable bowel syndrome (IBS). This follows the trend of first evaluating new gastrointestinal (GI) prokinetic drugs in disorders where disrupted GI motility is known to exist, rather than in a functional bowel disorder where changes in motility are uncertain. If prucalopride is not progressed towards the IBS indication, it has at least shown the way for other selective 5-HT4 receptor agonists. Most notable among these is TD-5108 (velusetrag), also characterized by good selectivity at the 5-HT4 receptor, high intrinsic activity and efficacy in patients with chronic constipation.

New pharmacologic therapies in gastrointestinal disease

Many gastrointestinal diseases remain poorly responsive to therapies, and even in the cases of conditions for which there are many effective drugs, there is still considerable room for improvement. This article is focused on drugs for digestive disorders that have entered the marketplace recently, or are expected to reach the marketplace within the next 1 to 2 years. Although advances have been made in understanding gastrointestinal motility, visceral pain, mucosal inflammation, and tissue repair, the major gastrointestinal diseases remain as significant therapeutic challenges.

[New drugs for the treatment of constipation]

This review introduces new therapeutic options in the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation. Therefore, prucalopride and lubiprostone are discussed including their mechanisms and side effects. In addition, other substances that are currently under evaluation such as renzapride and linaclotide are described, since recent results showed a significant effect in patients with constipation. Thus, after the withdrawal of tegaserod due to cardiac side effects, new potent drugs are now available for the treatment of constipation.

New-generation 5-HT4 receptor agonists: potential for treatment of gastrointestinal motility disorders

IMPORTANCE OF THE FIELD

Gastrointestinal (GI) dysmotility is an important mechanism in functional GI disorders (FGIDs) including constipation, irritable bowel syndrome, functional dyspepsia, and gastroparesis. 5-hydroxytryptamine(4) (5-HT(4)) receptors are targets for the treatment of GI motility disorders. However, older 5-HT(4) receptor agonists had limited clinical success because they were associated with changes in the function of the cardiac HERG potassium channel.

AREAS COVERED IN THIS REVIEW

We conducted a PubMed search using the following key words alone or in combination: 5-HT(4), safety, toxicity, pharmacokinetics, pharmacodynamics, clinical trial, cardiac, hERG, arrhythmia, potassium current, elderly, prucalopride, ATI-7505, and velusetrag (TD-5108), to review mechanisms of action, clinical efficacy, safety and tolerability of three new-generation 5-HT(4) receptor agonists.

WHAT THE READER WILL GAIN

Prucalopride, ATI-7505, and velusetrag (TD-5108) are highly selective, high-affinity 5-HT(4) receptor agonists that are devoid of action on other receptors within their therapeutic range. Their efficacy has been demonstrated in pharmacodynamic studies which demonstrate acceleration of colonic transit and, to a variable degree, in clinical trials that significantly relieve chronic constipation. Currently available evidence shows that the new 5-HT(4) receptor agonists have safe cardiac profiles.

TAKE HOME MESSAGE

New-generation 5-HT(4) receptor agonists and future drugs targeting organ-specific splice variants are promising approaches to treat GI dysmotility, particularly colonic diseases.

Role of prucalopride, a serotonin (5-HT(4)) receptor agonist, for the treatment of chronic constipation

Constipation affects up to a quarter of the population in developed countries and is associated with poor quality of life and significant economic burden. Many patients with chronic constipation are dissatisfied with current therapy due to lack of long-term efficacy or side effects. Previous nonselective 5-hydroxytryptamine receptor 4 (5-HT₄) agonists have been associated with significant interactions with other receptors (5-HT_1B, 5-HT_1D, and 5-HT_2B for tegaserod; hERG for cisapride), leading to adverse cardiovascular events resulting in withdrawal of these drugs from the market. Prucalopride is a novel gastrointestinal prokinetic agent. It acts as a high affinity, highly-selective 5-HT₄ agonist. Its efficacy in patients with chronic constipation has been demonstrated in several phase II and phase III clinical trials showing significant improvements in bowel transit, bowel function, gastrointestinal symptoms, and quality of life, with benefit maintained for up to 24 months in open label, multicenter, follow-up studies. Prucalopride’s high selectivity for the 5-HT₄ receptor may explain its favorable safety and tolerability profiles, even in elderly subjects with stable cardiovascular disease. Prucalopride is a well tolerated and efficacious prokinetic medication that should enhance the treatment of chronic constipation unresponsive to first-line treatments.

Safety assessment of prucalopride in elderly patients with constipation: a double-blind, placebo-controlled study

Chronic constipation is common among nursing home residents. The aim of this study was to evaluate safety, tolerability and pharmacokinetics of the selective 5HT(4) receptor agonist prucalopride in elderly, chronically constipated patients in nursing homes. A multicentre, phase II, randomized, double-blind dose-escalation study in 89 elderly constipated nursing home residents treated with placebo, 0.5, 1 or 2 mg prucalopride once daily for 28 days was analysed. Adverse events, vital signs, ECG, Holter monitor and pharmacokinetics were assessed (Clinicaltrials.gov identifier: NCT00627692). Patients' mean age was 83 years; 88% had a history of cardiovascular diseases. Most frequent adverse events, at least possibly related to prucalopride, were diarrhoea and abdominal pain. Relative to placebo, there were no differences in vital signs, ECG corrected QT interval, ECG morphology parameters, or incidence of supraventricular or ventricular arrhythmias on Holter monitoring. Plasma prucalopride concentrations increased proportionally with administered dose. Prucalopride up to 2 mg once daily for 4 weeks was safe and well-tolerated by constipated elderly patients, with no differences vs placebo in ECG or a range of Holter-monitoring parameters.

Pharmacological and electrophysiological characterization of nine, single nucleotide polymorphisms of the hERG-encoded potassium channel

BACKGROUND AND PURPOSE

Potencies of compounds blocking K(V)11.1 [human ether-ago-go-related gene (hERG)] are commonly assessed using cell lines expressing the Caucasian wild-type (WT) variant. Here we tested whether such potencies would be different for hERG single nucleotide polymorphisms (SNPs).

EXPERIMENTAL APPROACH

SNPs (R176W, R181Q, Del187-189, P347S, K897T, A915V, P917L, R1047L, A1116V) and a binding-site mutant (Y652A) were expressed in Tet-On CHO-K1 cells. Potencies [mean IC(50); lower/upper 95% confidence limit (CL)] of 48 hERG blockers was estimated by automated electrophysiology [IonWorks HT (IW)]. In phase one, rapid potency comparison of each WT-SNP combination was made for each compound. In phase two, any compound-SNP combinations from phase one where the WT upper/lower CL did not overlap with those of the SNPs were re-examined. Electrophysiological WT and SNP parameters were determined using conventional electrophysiology.

KEY RESULTS

IW detected the expected sixfold potency decrease for propafenone in Y652A. In phase one, the WT lower/upper CL did not overlap with those of the SNPs for 77 compound-SNP combinations. In phase two, 62/77 cases no longer yielded IC(50) values with non-overlapping CLs. For seven of the remaining 15 cases, there were non-overlapping CLs but in the opposite direction. For the eight compound-SNP combinations with non-overlapping CLs in the same direction as for phase 1, potencies were never more than twofold apart. The only statistically significant electrophysiological difference was the voltage dependence of activation of R1047L.

CONCLUSION AND IMPLICATIONS

Potencies of hERG channel blockers defined using the Caucasian WT sequence, in this in vitro assay, were representative of potencies for common SNPs.

Prucalopride: a new drug for the treatment of chronic constipation

Prucalopride belongs to a novel class of 5-hydroxytryptamine-4 receptor agonists, and has been evaluated extensively for the treatment of chronic constipation. Prucalopride has a stimulatory effect on gastrointestinal motility and transit, as established by in vivo and in vitro studies in animals and humans. Its therapeutic efficacy, tolerability and safety have been evaluated in Phase II and Phase III studies in chronic constipation. The cardiovascular safety profile of the drug was studied in vitro and in vivo in animal studies, in clinical studies in chronic constipation patients, as well as in specific additional clinical cardiovascular studies. Phase II studies identified a dose-dependent effect of prucalopride on bowel pattern and associated symptoms in chronic constipation. The Phase III studies mainly recruited patients with insufficient response to laxatives, and showed consistent efficacy and excellent tolerability for prucalopride.

Collation, assessment and analysis of literature in vitro data on hERG receptor blocking potency for subsequent modeling of drugs' cardiotoxic properties

The assessment of the torsadogenic potency of a new chemical entity is a crucial issue during lead optimization and the drug development process. It is required by the regulatory agencies during the registration process. In recent years, there has been a considerable interest in developing in silico models, which allow prediction of drug-hERG channel interaction at the early stage of a drug development process. The main mechanism underlying an acquired QT syndrome and a potentially fatal arrhythmia called torsades de pointes is the inhibition of potassium channel encoded by hERG (the human ether-a-go-go-related gene). The concentration producing half-maximal block of the hERG potassium current (IC(50)) is a surrogate marker for proarrhythmic properties of compounds and is considered a test for cardiac safety of drugs or drug candidates. The IC(50) values, obtained from data collected during electrophysiological studies, are highly dependent on experimental conditions (i.e. model, temperature, voltage protocol). For the in silico models' quality and performance, the data quality and consistency is a crucial issue. Therefore the main objective of our work was to collect and assess the hERG IC(50) data available in accessible scientific literature to provide a high-quality data set for further studies.

Blockade of HERG K+ channel by isoquinoline alkaloid neferine in the stable transfected HEK293 cells

We studied the effects of isoquinoline alkaloid neferine (Nef) extracted from the seed embryo of Nelumbo nucifera Gaertn on Human ether-à-go-go-related gene (HERG) channels stably expressed in human embryonic kidney (HEK293) cells using whole-cell patch clamp technique, western blot analysis and immunofluorescence experiment. Nef induced a concentration-dependent decrease in current amplitude according to the voltage steps and tail currents of HERG with an IC(50) of 7.419 microM (n(H) -0.5563). Nef shifted the activation curve in a significantly negative direction and accelerated recovery from inactivation and onset of inactivation, however, slowed deactivation. In addition, it had no significant influence on steady-state inactivation curve. Western blot and immunofluorescence results suggested Nef had no significant effect on the expression of HERG protein. In summary, Nef can block HERG K(+) channels that functions by changing the channel activation and inactivation kinetics. Nef has no effect on the generation and trafficking of HERG protein. A blocked-off HERG channel was one mechanism of the anti-arrhythmic effects by Nef.

A placebo-controlled trial of prucalopride for severe chronic constipation

BACKGROUND

In this 12-week trial, we aimed to determine the efficacy of prucalopride, a selective, high-affinity 5-hydroxytryptamine4 receptor agonist, in patients with severe chronic constipation.

METHODS

In our multicenter, randomized, placebo-controlled, parallel-group, phase 3 trial, patients with severe chronic constipation (< or =2 spontaneous, complete bowel movements per week) received placebo or 2 or 4 mg of prucalopride, once daily, for 12 weeks. The primary efficacy end point was the proportion of patients having three or more spontaneous, complete bowel movements per week, averaged over 12 weeks. Secondary efficacy end points were derived from daily diaries and validated questionnaires completed by patients. Adverse events, clinical laboratory values, and cardiovascular effects were monitored.

RESULTS

Efficacy was analyzed in 620 patients. The proportion of patients with three or more spontaneous, complete bowel movements per week was 30.9% of those receiving 2 mg of prucalopride and 28.4% of those receiving 4 mg of prucalopride, as compared with 12.0% in the placebo group (P<0.001 for both comparisons). Over 12 weeks, 47.3% of patients receiving 2 mg of prucalopride and 46.6% of those receiving 4 mg of prucalopride had an increase in the number of spontaneous, complete bowel movements of one or more per week, on average, as compared with 25.8% in the placebo group (P<0.001 for both comparisons). All other secondary efficacy end points, including patients' satisfaction with their bowel function and treatment and their perception of the severity of their constipation symptoms, were significantly improved with the use of 2 or 4 mg of prucalopride as compared with placebo, at week 12. The most frequent treatment-related adverse events were headache and abdominal pain. There were no significant cardiovascular effects of treatment.

CONCLUSIONS

Over 12 weeks, prucalopride significantly improved bowel function and reduced the severity of symptoms in patients with severe chronic constipation. Larger and longer trials are required to further assess the risks and benefits of the use of prucalopride for chronic constipation. (ClinicalTrials.gov number, NCT00483886 [ClinicalTrials.gov].).